I have no trouble with the composite class thing - in fact, in my dd1's first school for P1 she was in a Gaelic unit in a school and was in a p1-7 class of 8 pupils - and it was fabulous! I would highly recommend Gaelic education - the linguistic and cultural elements are both fantastic.
I have children in p2, 3 and 5 at Sgoil Ghaidlig Ghlaschu and it is great. I think there is more of a problem with "sniffiness" in bigger schools are there are more people to be sniffy with, tbh. There were mums at the nursery esp when my ds was there who never spoke in English at all adn woudl address you in Gaelic even when they knew you were a learner/non speaker, every time. Which I did find a bit rude. Its not a big problem, but it is there. It was a much bigger problem in Lewis!
I have done my total best to learn Gaelic. I've done 2 lots of classes and worked really hard at it and I am good at languages, but I have never got to grips with speaking it. I do know more than just the phonics, and can understand a good bit of what my kids say/read, but have had to accept I will never be fluent, I just don't seem to be able to make it happen!!! But I want the children to have the language/culture, and have been amazed at what they have picked up - d1 in p5 is fluent, as is ds in p3, pretty much. Dd2 has found it a little harder going but is doing well too. Dd1 plays the accordion at school and ds the chanter.
Just spoke to dd1 who came through to see what I am doing. I asked her if anyone should send their kids to Gaelic school. Her answer was "yes yes yes yes yes and a million times yes!!!" (Tha tha tha tha tha ceud tursann tha!)